Some viscous products, including for example, adhesives, caulks, and sealants, are commonly packaged in product cartridges or tubes. These tubes typically include a cardboard or plastic cylindrical body. Generally, a dispensing nozzle is located at one end of the tube and at the other end of the tube is a piston that operates as a moveable wall. These product cartridges are typically inserted into a dispensing device that includes some mechanism for exerting a force on the movable wall to push product from the product cartridge.
The force exerting mechanism has traditionally been a trigger that mechanically cooperates with a shaft to drive the shaft against the movable wall. Pneumatic pressure has also been suggested as an alternative force exerting mechanism. At the end of a dispensing operation, the product within the cartridge can remain pressurized which causes product to continue to be dispensed beyond that desired by the user. Consequently, nozzle valves have been provided in such pneumatic dispensing devices to provide the user more controlled termination of product dispensing.
The nozzle valve has generally been linked to a manually operated trigger that also controls the flow of the pneumatic fluid. The driving linkage between the trigger and the nozzle valve, however, has typically not been very robust. For example, product in the nozzle can begin to harden between uses such that the drive linkage is incapable of developing sufficient driving force to actuate the nozzle valve. In addition, in some instances attempts to actuate the trigger can actually cause damage to the drive linkage, making the dispensing device inoperable. Accordingly, a robust drive linkage for the nozzle valve is desirable.